Lubricating oil compositions containing improved sludge inhibiting additives

ABSTRACT

Mineral lubricating oil compositions are prepared containing sludge dispersing amounts of conventional ashless dispersants and, optionally, their sulfurized derivatives, and also containing sludge inhibiting or oxidation inhibiting amounts of sulfurized oil-soluble pour point depressant type organic compounds. The ashless dispersants used are the polyalkylene polyamine condensation products of alkenyl succinic acids or anhydrides or of alkenyl substituted lower fatty acids wherein the alkenyl radical is of C40 to C250 length used either alone or along with their sulfurized derivatives. The pour point depressants are those heretofore conventionally used but in their sulfurized form, such as sulfurized wave alkylated naphthalene, sulfurized polymeric long chain alkyl esters of acrylic or methacrylic acids.

United States Patent LUBRICATING OIL COMPOSITIONS CONTAINING IMPROVEDSLUDGE INHIBITING ADDITIVES Sliih-En Hu, Westfield, NJ.

Esso Research and Engineering Company Feb. 19, 1970 Int. Cl. ..Cl0m l/38Field of Search ..2S2/47.5, 51.5, 45, 48.6, 406

References Cited UN lTED STATES PATENTS 11/1966 Le Suer ..2S2/5l.5 A

3/1968 Le Suer et a1... 6/1968 Ol-lalloran..... 7/1969 Le Suer et a1.3/1970 Smith Rogers et al. Jones et al ..252/45 1 July 11, 1972 FOREIGNPATENTS OR APPLlCATIONS 952,151 3/1964 Great Britain OTHER PUBLICATIONSKalichevsky et al. Petroleum Refining with Chemicals" (1956) pages 525-534 Primary Examiner-Daniel E. Wyman Assistant Examiner-W. CannonAttorney-Pearlman and Stahl and Ernest V. Haines ABSIRACT Minerallubricating oil compositions are prepared containing sludge dispersingamounts of conventional ashless dispersants and, optionally, theirsulfurized derivatives, and also contain ing sludge inhibiting oroxidation inhibiting amounts-of sulfurized oil-soluble pour pointdepressant type organic com pounds. The ashless dispersants used are thepolyalkylene polyamine condensation products of alkenyl succinic acidsor anhydrides or of alkenyl substituted lower fatty acids wherein thealkenyl radical is of C to C length used either alone or along withtheir sulfurized derivatives. The pour point depressants are thoseheretofore conventionally used but in their sulfurized form, such assulfurized wave alkylated naphthalene, sulfurized polymeric long chainalkyl esters of acrylic or methacrylic acids.

7Claims, No Drawings LUBRICATING OIL COMPOSITIONS CONTAINING IMPROVEDSLUDGE INHIBITING ADDITIVES The present invention relates to the use inmineral lubricating oil compositions of a combination of oil-solublesulfurized pour point depressant-type compounds with the so-calledashless dispersants which are likewise oil-soluble and which have beenused in lubricating oil compositions for several years. In addition, theadditive admixtures may contain sulfurized ashless dispersants of thesame or different ashless dispersants used.

Numerous addition agents have heretofore been prepared for use inmineral lubricating oils including the so-ca1led heavy duty oils whichare employed in railroad diesel engines and gas engines. Priorresearchers have been successful in finding various types of oil-solubleorganic compounds which exhibit speciali zed and specific properties ofa beneficial nature when they are incorporated into mineral lubricatingoils. For many years now, organic compounds have been added in minoramounts to lubricating oils for the purpose of lowering their pourpoint, of improving their viscosity index, of affording increasedresistance to oxidation, of imparting antiwear properties, of inhibitingsludge formation and of dispersing sludge when it is formed during useof the oils. The use of such additives at the present time enjoyswidespread commercial acceptance. Good oxidation stability and gooddispersing along with good detergency have become essential requirementsfor engine lubricating oils. This is particularly so in connection withlubricating oils used in so-called heavy duty engines such as gasengines and railroad diesel engines. Additionally the additives employedmust necessarily be accepted from the standpoint of lack of wear orattack on the specialized types of bearings employed in internalcombustion engines at the present time. Copper-lead containing bearingsare usually susceptible to wear and corrosion and suitable compoundedoils must exhibit low corrosion and low bearing wear with respect tosuch specialized bearings in order to be acceptable commercially.

In the past, it has been proposed to add sulfurized polyisobutylene tolubricating oils. See, for example, Cohen U.S. Pat. No. 2,312,750. Also,it has been proposed in the past to employ sulfurized ashlessdispersants in lubricating oils, see British Pat. No. 1,101,040 and U.S.Pat. No. 3,390,086.

By incorporating elemental sulfur into oil-solublepourpoint-depressant-type organic compounds, many of which have beenconventionally used heretofore as pour point depressants, it is possibleto impart, in addition to the pour point properties, (which are notmaterially sacrified) anti-oxidant properties as well, so that even inthe case of lubricating oil compositions being subjected to extremelyhigh temperatures during use the combined or dual properties areutilized. It has now been discovered that the tendency of formation ofsludge and other deposits in lubricating oils is lessened or minimizedby using, in combination in such lubricating oils, at least twoadditives, namely an ashless dispersant which tends to disperse sludgeand to prevent its deposition in the engine and a sulfurized pour pointdepressant or a sulfurized compound closely akin to such depressantswhich has anti-oxidant properties and which imparts an initial and addedresistance to sludge formation through oxidation inhibition. Such acombination of additives leads to an enhanced elimination of thetendency to form sludge by chemical reduction of the sludge precursorsin addition to the usual dispersion of the sludge that is formed. It hasbeen discovered, however, there is a synergistic enhancement of thedesired properties in lubricating oils when these two types of materialsare used together in a mineral lubricating oil composition.

Although it is not necessary that the pour point depressant types ofcompounds in and of. themselves possess pour point depressant propertieswhen added to lubricating oils, the present invention finds its greatestutility when conventional pour point depressant compounds are subjectedto a reaction with elemental sulfur, for it has been discovered that thepour point depressant properties of such compounds which have beenconventionally employed in the past are not destroyed but in addition bythe introduction of the elemental sulfur into a chemical bond with suchcompounds additional properties are imparted to these pour pointdepressants, namely antioxidant and sludge precursor destroyingproperties which tend to minimize and decrease the normal tendency ofsuch oils to degradative oxidation and hence sludge formation. Othercompounds may be employed, i.e. compounds other than those which intheir unsulfurized form do, in fact, depress the pour point of suchmineral lubricating oils. These compounds are referred to as pour pointdepressant type compounds because their chemical comfiguration isanalogous to the chemical configuration of the compounds which dopossess pour point depressant properties and they are homologues oranalogues thereof which are oil-soluble. Both types of compounds, i.e.pour depressants and the closely related compounds not possessing pourpoint depressant properties, are intended to be included in theexpression pour point depressant type compound or the expression pourpoint depressant type organic compound as used herein and in the claims.

The types or classes of compounds that may be treated with elementalsulfur or its chemical equivalent, i.e. sodium polysulfide, for example,are all oil-soluble and have generally number average molecular weightsof between about 900 and about 20,000, preferably between about 1200 andabout 10,000. They may be broadly defined in the following classes:

1. long chain C,,C alkylated-benzene, -phenols, naphthalene, -naphthols,i.e. paraffin-wax-alkylated naphthalene, wax alkylated phenol;

2. long chain (C -C alkylated C C alkyl substituted benzene,naphthalene, phenol, or naphthol compounds, i.e. paraffin-wax-alkylatedcresols, wax-alkylated toluene, wax-alkylated alpha or beta methylnaphthalene, wax alkylated 1- methyl beta naphthol, etc.;

3. polymers of C C alkyl esters of monoolefinically unsaturatedmonocarboxylic acids, e.g. acrylic, methacrylic, or vinyl acetic acidesters of butyl, amyl, hexyl, decyl, lauryl, cetyl or stearyl alcohols;polylauryl acrylate, polymers of mixed C, C, (Lorol) alcohols esterifiedwith acrylic acid or methacrylic acids;

4. polymers of C -C dialkyl or dialkenyl esters of alphabeta unsaturateddibasic carboxylic acids or anhydrides thereof, e.g. maleic or fumaricacid esterified with octyl alcohol or C oxo alcohols, di-Lorolfumarates, didodecyl maleate;

5. polymeric C -C acylated polystyrene, e.g. bchenyl polystyrene; acetylwax alkylated polystyrene;

6. polyacryl amides, i.e. N-vinyl pyrrolidone or N-vinyl pyrrolidonecopolymerized with C C fatty acids, polymeric N- octadecylmethacrylamide, N-octadecenyl polyethylacrylamides;

7. copolymers of vinyl esters of C C fatty acids, or C C alphamonoolefins, with monomers of (4) i.e. di C -C dialkyl esters of alphabeta unsaturated dicarboxylic acids or anhydrides; copolymers ofdi-Lorol (C |s) fumarate with vinyl acetate, copolymers of di C alkylfumarate with isobutylene.

All of the above-mentioned classes of compounds are old compositions,most of which have heretofore been used in automotive and marine enginesas additives in crankcase lubricants. Their sulfurized derivatives arethe novel additives in such crankcase lubricants as described, supra.Various U.S. patents described the methods of preparation and thelubricating oil additive usage of these unsulfurized compounds, forexample, group (1) and (2) compounds have been used for many years aspour point depressants as exemplified by the disclosures ofU.S. Pat.Nos. 1,815,022; 2,015,748; 2,087,682; 2,174,246 and 2,191,498; group (3)compounds by U.S. Pat. Nos. 2,100,993; 2,125,885 and 2,628,225; group(4) compounds by U.S. Pat. No. 2,618,602; group (5) compounds by U.S.Pat. Nos. 2,703,817 and 3,248,186; group (6) compounds by U.S. Pat. No.2,387,501 and group (7) compounds by U.S. Patents Nos. 2,666,746;2,721,877; 2,721,878;

2,694,685; 2,825,717 and Reissue 26,134, which disclosures areincorporated herein by reference. No real need is seen for duplicatingthe description of the usage of the unsulfurized pour point depressantsin lubricating oils, herein, nor for duplicating, herein, their methodsof production, since they are well known; they have becomecommercialized and widely marketed additives for their pour pointdepressant efiects and have now been so used for many years. Thestarting materials, i.e. the materials to be sulfurized in accordancewith the present invention are old and widely available on thecommercial market.

The pour point depressant type organic compounds are subjected toreaction with elemental sulfur in order to chemically combine the sulfurinto the compound. The elemental sulfur or its chemical equivalent, forexample, sodium polysulfide, is added in the required amounts and thereacting mixture is maintained at a temperature between about 100 and260 C., preferably between about 120 and 250 C. for a period of timeranging between about 30 minutes and 40 hours, preferably for betweenabout 4 and about 12 hours. The relative amount of elemental sulfuremployed per mole of pour point dispersant type organic compounds usedmay vary considerably but is generally between about 2 and about 0.5mole of sulfur, preferably between about 1 and about 0.5 mole of sulfurper mole of organic compound to be sulfurized. The final product willcontain sulfur to the extent of between about 1.0 and about 10.0 wt.percent, preferably between about 1.5 and about 7.5 wt. percent sulfur.The sulfurization reaction is preferably carried out in the liquidphase. A particularly convenient liquid reaction medium has been foundto be a mineral lubricating oil for the reason that the sulfurizedproduct upon completion of the sulfurization reaction is present in thelubricating oil to the extent of some 50-80 wt. percent and so theentire reaction mixture once it has been purged of hydrogen sulfide bysweeping with nitrogen or other inert gas is suitable for use as an oilconcentrate. A typical oil base that has been used as a carrier for thereaction is a solvent extracted neutral lubricating oil of 150 SUS at100 F. To some extent this oil also is sulfurized but its small amountof sulfurization is not beneficial, per se. The ashless dispersant withor without the addition of sulfurized ashless dispersant may be added tothis concentrate. When a lubricating oil concentrate of the sulfurizedpour point type organic compound is finally produced or is compounded,the oil-soluble ashless dispersant as well as the sulfurized ashlessdispersant, if used, may be added as such or it may be added in the formof a similar solvent neutral 150 SUS base lubricating oil concentrate offrom 50-80 wt. percent active ingredient concentration. The amount ofthe sulfurized pour depressant type organic compound, the amount of theoil-soluble ashless dispersant and the amount of the sulfurized ashlessdispersant finally employed in a lubricating oil composition may varyconsiderably. Suffice it to say that these concentrations aresufficiently large to impart sludge inhibiting, dispersing and/orantioxidant properties to the lubricating oil. The amount involved sofar as the upper limit is concerned, is relatively immaterial so long asthe minimum effective amount is employed. For practical purposes, allthree types of additives are each employed (when employed) in an amountranging from 0.05 to 10.0 wt. percent based on the total oilcomposition, preferably between about 0.1 and about 5.0 wt. percent onthe same basis.

The oil-soluble ashless dispersants employed are those conventionallyemployed in lubricating oil compositions. In general, they are formed bya condensation of at least one polyalkylene polyamine with at least oneof the following: alkenyl succinic acid, alkenyl succinic anhydride,alkenyl substituted lower fatty acid, wherein the alkenyl group containsfrom about 40 to about 250 carbon atoms per alkenyl radical. Also, thesulfurized derivatives of such oil-soluble ashless dispersant may beused as before stated and as heretofore referred to as being disclosedin British Pat. No. 1,101,040 and U.S. Pat. No. 3,390,086. These patentsnot only disclose the production of the sulfurized ashless dispersantsof the type herein contemplated for use but also disclose severalmethods of preparing the unsulfurized ashless dispersants of thepolyalkylene polyamine-alkenyl succinic anhydride or alkenyl fatty acidcondensation type. The disclosure of U.S. Pat. No. 3,390,086 isincorporated herein by reference not only as to the sulfurizeddispersants but also to lend support and basis for the preparation anduse of the unsulfurized ashless dispersants therein disclosed. TheAnderson patents and the LeSuer U.S. Pat. Nos. 3,185,646; 3,185,647;3,200,107 and 3,216,936 are also incorporated herein by reference. Theyshow the preparation and use of these unsulfurized ashless dispersants.The number average molecular weight of the ashless dispersants willgenerally be between about 700 and about 5,000, preferably between about800 and about 2,000 and preferably the alkenyl radical constitutes apolyisobutylene or a polypropylene having the requisite 40-250 carbonatoms per radical. An example of a suitable alkenyl lower fatty acidwhich is condensed with a polyalkylene polyamine is polyisobutenylpropionic acid. This is formed by halogenating the polyisobutylene andcondensing it with acrylic acid or an analog, such as alphamethylacrylic acid, crotonic or isocrotonic acid. The polyisobutenylsuccinic anhydride or polyisobutenyl succinic acid is obtainedconventionally by condensing the polyisobutylene orchloropolyisobutylene with maleic or fumaric acids or maleic anhydride.

The polyalkylene polyamines which are reacted with the carboxylic acidsor their anhydrides encompass a considerable number of compounds and arefully described under the heading Ethylene Amines in Encyclopedia ofChemical Technology, Kirk & Othmer, Volume 5, pages 898-905 (1950). Anynumber of specific polyethylene polyamines are available in commerce andmarketed. A preferred polyamine which is widely used in preparing theashless dispersant type condensation products is tetraethylenepentamine.One method of preparing the condensation products of, for example,polyisobutenyl succinic anhydride and tetraethylene-pentamine isdisclosed in U.S. Pat. No. 3,172,892 and this material is the materialwhich has been used as the ashless dispersant additives in thehereinafter described specific examples.

The lubricating oils employed as the base oils are preferably minerallubricating oils which may be derived from naphthenic, parafiinic,aromatic, or mixed crude oils. Generally they will have a viscosity at210 F. of between about 45 and about SUS (Saybolt Universal Seconds) andat F. a viscosity of between about and about 1,100 SUS. The viscosityindices of these oils will generally range between about 0 and about100. in the case of oils employed in high speed, heavy duty dieselengines, oils of high viscosity indices are often preferred, i.e. of theorder of 100 or higher. Usually most diesel engines employ lubricatingoils having viscosities of between about 75 and about 80 SUS at 210 F.and at 100 F. of between about 800 and about 1,250 SUS, with viscosityindices ranging between about 55 and about 80.

Amounts similar to the amounts specified for the novel additives arelikewise employed for the conventional additives which are also used insuch lubricating oils. These additives are corrosion inhibitors,(sorbitan mono-oleate), antioxidants, (N-phenyl alpha naphthylamine)pour point depressants, (unsulfurized wax alkylated naphthalene),viscosity index improvers (unsulfurized polyisobutylene or polymethylmethacrylates), antiwear agents (the zinc salt of di (C ,-C 5 alkyl)dithiophosphate), detergents (the alka-line earth metal salts of alkylsubstituted phenol thioethers or sulfides), and dispersants (alkalineearth metal salts of petroleum sulfonic acids or of alkaryl sulfonicacids and the like.

The following examples are illustrative of the character and nature ofthe invention but it is not intended that the invention be limitedthereto.

EXAMPLE 1 About 400 grams of paraffin wax alkylated naphthalene, whichis conventionally employed as a pour point depressant for lubricatingoils, was reacted with about 8 grams of sulfur at a temperature of 180C. (356 F.) for 7 hours. After filtration of the product, the filtrateanalyzed about 1.42 wt. percent of sulfur.

The resultant material and the starting material were both subjected toa series of comparative sludge inhibition tests in which the base oilcomposition involved the use of a sludgecontaining used oil which wasfreed of solid sludge by centrifuging for one hour at 1,800 rpm. Tengrams of the supematant oil freed of solid sludge particles, butcontaining oil-soluble sludge precursors, was employed as the base oilin this test. The oil, without any further additives, upon heating tothe temperature applied in the test, would tend to form additionaloil-insoluble deposits of sludge. In a tared stainless steel centrifugetube, 10 grams of the supernatant used oil containing 1.0 wt. percent ofthe additive to be tested with or without 0.4 wt. percent of an ashlessdispersant was heated to 150". C. (300 F.) for 2 hours in a constanttemperature oil bath. Following the heating, the tube was cooled andthen centrifuged for one hour at 1,800 rpm. The supernatant oil wasdecanted again from the tube and any residual sludge deposits werewashed carefully with 99 percent n-pentane to remove all remaining oilassociated therewith. The weight of the solid sludge formed during thetest was determined. Blank or other comparative runs were also carriedout in which either no additive was employed or an additive, to becompared, was employed. A substantial decrease in the amount of sludgedeposited, as compared with the amount deposited in the case of theblank run, indicates the extent, if any, that the additives had a sludgeinhibition effect, through the actual measurement, in milligrams, of theweight of the sludge formed. The following comparative data wereobtained:

Note: Run F additive was prepared by reacting the unsulfurized solvent150 neutral oil (400 grams) with elemental sulfur (16 grams) at 180 C.for 10 hours and stripping the reacted mixture with nitrogen at 120 C.for 1 hour. The product analyzed 1.42 wt. percent of sulfur. The blankused oil showed 10.5 mg. of sludge per 10 grams of oil.

It is apparent from these data that the use of sulfurized wax alkylatednaphthalene in combination with the ashless dispersant which isidentified as being formed by condensing polyisobutenyl succinicanhydride with tetraethylenepentamine as disclosed in US. Pat. No.3,172,892 (a conventionally marketed and commercially available ashlessdispersant) resulted in the production of less sludge under theconditions of testing than did the use of any other combination ofsulfurized or unsulfurized materials with or without the presence of theashless dispersant.

EXAMPLE 2 150 grams of the copolymer of di-Lorol fumarate and vinylacetate as a 50 percent concentrate in solvent neutral 150 minerallubricating oil having molecular weights of about 10,000 (this can varybetween 8000 and 12,000) was reacted with 7.5 grants of elemental sulfurat a temperature of 180 C. for about 6 k hours. The unreacted sulfur wasremoved from the reacted mixture by filtration. The filtrated producthad a combined sulfur content of about 1.75 wt. percent.

The sludge inhibition test described in Example 1 was carried out usingthe same used oil containing sludge precursors as was employed to securethe data in Table l. The used oil containing 1 percent of the sulfurizedproduct of Example 2 showed a sludge formation of 7.1 mg. per 10 gramsof used oil while the used oil containing no sulfurized product showedthe formation of 10.5 mgs. of sludge per 10 grams of used oil.

EXAMPLE 3 grams, as a 60 percent concentrate in lubricating oil, of apolymer of the ester formed by esterifying a mixture of methacrylic acidwith a mixed C, C,,, alcohol fraction and having the molecular weight ofabout 10,000 was sulfurized with 7.5 grams of elemental sulfur at atemperature of C. for about 6.5 hours. The unreacted sulfur was removedby filtration and the filtrate had a combined sulfur content of 1.73 wt.percent.

The same sludge inhibition test on used oil, as described in Example 1,was undertaken on a comparative basis with and without the presence of aconventional ashless dispersant. The comparative data are as follows:

dispersant as shown in Table l, i.e. the condensation product ofpolyisobutenyl succinic anhydride with tetraethylenepentamine and wasused as a 70 percent concentrate in mineral lubricating oil in securingthe data in Table 1.

EXAMPLE 4 56 grams as a 50 percent oil concentrate of C C acylated(behenyl) polystyrene having a molecular weight of about 5,000 wassulfurized with about 6 grams of elemental sulfur at a temperature of200 C. for about 5 hours. The sulfurized material was extracted withabout 200 cc. normal heptane, filtered and stripped under nitrogenovernight. The recovered product had a combined sulfur content of about1.2 wt. percent.

The same inhibition-oxidation test involving used oil containing sludgeprecursors as was carried out and described in Example 1 was employed inthe following comparative runs:

TABLE 111 Sludge, Milligrams Per 10 Grams Used Run No. Oil

P 1% product of Example 4 14.3

Note: the same ashless dispersant as described in Tables 1 and 11 wasemployed in securing the data appearing in Table III.

It is apparent from the study of the comparative data appearing inTables II and III that the combination of using an ashless dispersanttogether with a sulfurized polymeric material having a sufficiently highmolecular weight to impart oil solubility and having a structuralconfiguration so as to give, in unsulfurized form, a pour pointdepressant effect gives unexpected oxidation-inhibition when used inmineral lubricating oils which normally have a tendency to form sludge.

What is desired to be secured by Letters Patent is:

What is claimed is:

l. A lubricating oil composition comprising a major proportion of amineral lubricating oil,

a minor sludge inhibiting amount of a sulfurized polymeric C, to C alkylester of acrylic or methacrylic acid, said ester having lubricating oilpour point depressant properties, said sulfurized ester containing about1 to wt. percent of sulfur,

and a minor sludge dispersing amount of at least one oilsoluble ashlesssludge dispersant selected from the group consisting of condensationproducts of polyalkylene polyamines with alkenyl succinic acid, alkenylsuccinic anhydride, and alkenyl propionic acid, wherein the alkenylradical has from about 40 to 250 carbon atoms.

2. A lubricating oil composition as defined by claim 1 wherein saidsulfurized ester and said ashless dispersant are each present in aconcentration between about 0.05 and about 10 wt. percent of the totalcomposition.

3. A lubricating oil composition as defined by claim 1 which alsocontains a minor sludge inhibiting amount of at least one sulfurizedashless dispersant wherein said ashless dispersant is as set forth inclaim 1.

4. A lubricating oil composition as defined by claim 1 wherein saidsulfurized polymeric ester is a sulfurized polymeric mixed C, C alkylmethacrylate.

5. A lubricating oil composition as defined by claim 1 wherein saidpolyalkylene polyamine is tetraethylene pentamine.

6. A lubricating oil composition as defined by claim 1 wherein saidalkenyl radical is polyisobutenyl.

7. A lubricating oil composition as defined by claim 1 wherein saidashless dispersant is the condensation product of tetraethylenepentamine and polyisobutenyl succinic anhydride.

2. A lubricating oil composition as defined by claim 1 wherein saidsulfurized ester and said ashless dispersant are each present in aconcentration between about 0.05 and about 10 wt. percent of the totalcomposition.
 3. A lubricating oil composition as defined by claim 1which also contains a minor sludge inhibiting amount of at least onesulfurized ashless dispersant wherein said ashless dispersant is as setforth in claim
 1. 4. A lubricating oil composition as defined by claim 1wherein said sulfurized polymeric ester is a sulfurized polymeric mixedC12-C18 alkyl methacrylate.
 5. A lubricating oil composition as definedby claim 1 wherein said polyalkylene polyamine is tetraethylenepentamine.
 6. A lubricating oil composition as defined by claim 1wherein said alkenyl radical is polyisobutenyl.
 7. A lubricating oilcomposition as defined by claim 1 wherein said ashless dispersant is thecondensation product of tetraethylene pentamine and polyisobutenylsuccinic anhydride.